1. Field of the Invention
The present invention is related to an alarm processing apparatus in a system having a standby redundancy, in which specific items are individually monitored, with identification being made with respect to one-time faults or dispersed fixed faults.
2. Description of the Related Art
In systems such as a transmission system, a banking system, or a seat reservation system, it is necessary for the system to have high reliability, matched to the operating mode and conditions. In these systems, to achieve the functions required by the system, extra constitutional elements or means (hereafter simply called units) which are considered essential are provided beforehand, with continuous operation maintained by successive reconfiguration of the system by elimination of faulty units.
In such a redundant system, there is an active type of redundancy, such as in the case of a dual configured system, in which redundant units continue to maintain mutual monitoring, with parallel operation as long as they are operating normally, but with automatic separation of a unit which is judged to be faulty, and standby redundancy, such as in a duplex (hot-standby) configured system, in which if the currently in-service unit of the redundant units fails, one of the standby units is switched in.
However, in a transmission system, in the case of active redundancy, because the reliable mutual verification of the operating conditions of the units not only requires special logic, but is also expensive, it is difficult to apply. Because of this, the n+1 spare or above-described duplex system of redundancy is often used. Also, such as system is configured with a number of unmanned stations which are installed at geographically separated locations.
In a transmission system provided in such an unmanned station, although one-time or dispersed faults caused by misoperation due to induction from lightning, improper synchronization because of variation in the quality of the transmission path, or operational errors in performing remote control will be successively detected by an alarm detection section, an alarm signal indicating a fixed fault will not be included. Therefore, it is possible to perform highly accurate maintenance on only unmanned stations judged as having fixed faults, thereby enhancing the efficiency of maintenance and operation.
In such an alarm processing apparatus as this, in the case in which a unit in service fails and the standby unit is switched to be the in-service unit, an inhibit circuit that inhibits the passage of such an alarm signal in response to the corresponding system configuration signal transmits the alarm signal given by the output of an alarm processing circuit to the subsequent stage. However, because the connection between the transmission path and the signal termination section of the standby unit is broken by means of the standby relay 722, a pseudo fixed fault which actually has not occurred will be indicated until the alarm detection section and alarm processing circuit make a response with respect to the restoration of the connection.